Filter rings must be dried in an oven to a constant mass prior to use.

• A. True
• B. Not required to oven-dry the rings
• C. False
• D. Must be oven-dried to a constant mass

Answer: (C)

Moisture corrections are only needed when the exact dry mass of an item affects the calculations. For filter rings in this procedure, the results don’t depend on knowing the ring’s precise dry weight. The rings act as a filtration medium, and the outcome is based on the filtrate or the residue, not on the ring’s initial dry mass. So oven-drying to a constant mass before use isn’t required. Just follow the method’s instructions for cleaning and readiness of the rings; drying to constant mass would only be necessary if the procedure specifically called for it or if the ring’s dry weight was part of a later weighing step.